Electric Vehicles (EVs) are growing in popularity for reasons such as a different driving experience, higher performance, better reliability and lower maintenance, lower operational cost, and the potential to decrease the environmental impact of transportation. Electricity is used exclusively to propel the vehicle, or can be used to assist other methods such as internal combustion engines (ICEs).
The main types of the EVs are battery electric vehicles (BEV), plug-in hybrid electric vehicles (PHEV) and hybrid electric vehicles (HEV). EVs use an electric motor for propulsion. Electric energy is stored in batteries using, e.g. lithium-ion technology or any other form of battery chemistry. Other forms of energy storage are applicable too, such as supercapacitors or fuel cells. The HEV and the PHEV combine a conventional combustion engine with an electric drive system. HEVs use typically regenerative breaking to charge the batteries. PHEV contains rechargeable batteries that can be fully charged by connecting a plug to an external electric power source. BEVs are all electric vehicle without an internal combustion engine. The BEV and the PHEV also enables a user to choose alternative energy for charging the batteries by choosing an external power source which is using, for example, solar or wind power to produce electricity.
A common problem with current PHEVs and BEVs using rechargeable batteries is the long charging time. In a typical case charging requires hours and there are also a lot of city center apartments without any plug-in capabilities for vehicles. There are some fast charging stations but also at these charging times are much longer compared with cars using combustion engines which can be quickly “charged” in fuel stations. Fast charging also means that batteries tend to wear out faster. Also energy density is not so high which means bigger and heavier batteries. Power losses are also higher with fast charging. Also charging an 80 kWh battery in for example 30 minutes sets such power requirements that it is not possible typically at a residential home.
Another problem is that fast charging sets extra requirements for an electric infrastructure which is already stretched to the limit in many countries. In many industrialized nations, spare capacity in the order of magnitude of 50% or more is available and predictable. However, these are also times of lowest human and economic activity, which would be when fast charging is of no use. Although a typical user would charge at home during night time, a user could still prefer sourcing his energy from a commercial station which might offer lower prices than available to residential users. Other options include positive discrimination of renewable energies. For these cases current charging times are not what users are expecting.
There are several different proposals for changing the batteries for BEVs to overcome the problem described above. Typically rechargeable cells are grouped as modules and each module consists of a plurality of cells. These modules are monitored and controlled as one entity. If needed, a module can be changed in a service station to another module containing charged cells to supply quickly energy for BEV. One issue is that the available size for the battery varies a lot of depending on the use case and it might not be rectangular: one module doesn't fit well to all the use cases. It is possible to have modules with different sizes and form depending on the use case, meaning service stations would have to stock different modules which do not make sense financially.
Examples of modular energy storage systems of the kind described above are disclosed in U.S. Pat. No. 7,948,207 and US 2012/094162. There are also many multicell battery designs available having the possibility to connect on and off individual cells of the battery. Examples of these kinds of designs are disclosed in CN 202535104, CN 102832646, U.S. Pat. Nos. 8,330,420 and 7,075,194.
There are also several proposals as to how to monitor individual cells and, based on the characteristics of individual cells, to configure systems dynamically. For example US 2010/0261043 proposes a system for a dynamically reconfigurable battery framework for a large-scale battery system. This solves a problem as to how individual cells can be monitored and controlled but this system do not fit if the requirement is to replace hundreds of the depleted cells quickly in service station to supply electric energy for BEVs, since the cells are located in a certain way in a battery pack. Other control, failure-detection, reconfiguration, bypass and lifecycle management systems for batteries are disclosed for example in US 2005/242776, US 2006/192529, EP 2582009 and U.S. Pat. No. 8,084,994. These systems suffer at least partly from the same disadvantages.
Thus, there is a need for improved solutions for quickly supplying electric energy to electric vehicles and other power-intensive battery-operated devices.